The surveillance of people in public spaces has become necessary for public security. There is an increasing need to inspect what individuals are carrying. There is a real need to detect explosives, weapons or even drugs on the street. On trains, it is in particular necessary to detect explosives or weapons. In stadia, in addition to these dangerous objects, it is useful to detect glass bottles or drugs in particular.
Present-day inspection solutions are unsatisfactory. Security forces have at their disposal:                Metal detectors, which of course cannot detect non-metallic objects such as explosives;        X-ray devices, which are usable for baggage for example, but not in open zones for public-health reasons;        Permission to stop and search, but such interventions are slow and may be contested.        